Surprisingly, the two known specimens of the pocket shark have never been studied to any extent until recently. Researchers, by taking a small tissue sample of the creature and using the vast specimen collection available at Tulane University’s Biodiversity Research Institute were able to place the specimen in the genus Mollisquama, a sleeper shark.
The first pocket shark was found 36 years ago in the Pacific Ocean off the coast of Peru. That specimen was a female, and has been languishing in a Russian museum ever since, The female shark was 40 cm. (16 inches) long and was taken at a depth of 330 meters (984 feet).
The latest specimen is a male and was taken in the Gulf of Mexico in 2010, along with a bunch of other sea creatures during a government research trip. A male, it is only 5 1/2 inches long and still bears an umbilical scar showing it had been recently born. This second specimen was used in the study.
The discovery of the two strange pockets
The little pocket shark specimen sat in NOAA’s holdings lab in Pascagoula from 2010 until very recently, when Tulane University researchers Michael Doosey and Henry Bart, and NOAA Ocean Service genetics expert Gavin Naylor, were asked to give the specimen a close-up examination.
The research team first identified the species and found the pocket shark is closely related to the kitefin and cookie cutter species, fellow members of the shark family Dalatiidae. The pocket shark, like other members of the Dalatidae family, might remove plugs of flesh from their prey when hungry.
Biologist Michael Doosey, says the shark is cute. “It almost looks like a little whale.” But the thing that really surprised the team was discovering two pockets next to its front fins. “I wasn’t really sure what it was,” Mark Grace said. “That pocket over on the pectoral fin, I had never seen anything like that on a shark.”
The two pouches on the shark are not quite like the pouch seen on a kangaroo, which uses its pouch to carry its young. Scientists really have no idea what the shark’s pouches are used for. It is unusual to find pouches as large as those on the shark specimen, which make up about four percent of its body.
The study was published in the journal of taxonomy Zootaxa on April 22, 2015 under the title: “First record of Mollisquama sp. (Chondrichthyes: Squaliformes: Dalatiidae) from the Gulf of Mexico, with a morphological comparison to the holotype description of Mollisquama parini Dolganov.”